This invention relates to a photoelectric converting device for forming a charge latent image with high resolution and a recording system thereof. In compliance with an increased demand for a reproduced image with high picture quality and high resolution in recent years, as well known, various systems such as so-called EDTV (Extended Definition TV) system, or HDTV (High Definition TV) system have been proposed for a television system. In order to obtain a reproduced image with high picture quality and high resolution, it is required to provide an image pickup device capable of producing a video signal from which a high picture quality and high resolution image can be recreated. However, for conventional image pickup devices using an image pickup tube, it is difficult to generate such a video signal. The reasons for this are as follows: Since there is a limit to the reduction of the diameter of an electron beam in the pickup tube, high resolution image reproduction by reduction of the diameter of the electron beam cannot be expected. Alternatively, if the target area of the pickup tube is increased, the level of the output signal will be reduced because of the increased output capacity which is proportional to the area of the target. Therefore, high resolution image reproduction by the increase of the target area cannot be realistic. Furthermore, in the case of an image pickup device for a moving picture, since the frequency range of such a video signal reaches several tens to several hundreds MHz for implementation of the high resolution image, the signal to noise ratio deteriorates.
As stated above, conventional image pickup devices could not satisfactorily generate such a video signal to provide a reproduced image of high picture quality and high resolution because of the inevitable use of an image sensor for the construction thereof. In order to solve this, the assignee of this application has already proposed a recording apparatus in which a charge latent image carrying information signals intended to be recorded, is formed in a photo-conductive layer member by projecting an optical image thereto corresponding to the information signals, the charge latent image is then transferred to a charge holding layer member of a recording medium. The recording medium is constructed by laminating, for example, the electrode and an insulating layer member acting as the charge holding layer member and the insulating layer member is composed of a material with extremely high insulation resistance, such as silicon resin, which is capable of holding the charge attached thereon for a long time.
The assignee of this application has also proposed a recording apparatus similar in principle to the previously explained apparatus, in which a charge latent image carrying information signals to be recorded is transferred to a charge holding layer of a recording medium by varying the electric field generated between a photo-conductive layer member and an electrode of the recording medium in accordance with the information signals.
In either of the proposed recording apparatuses, the surface of the photo-conductive layer member on which the charge latent image is firstly formed, and the surface of the charge holding layer member of the recording medium to which the charge latent image is secondary formed, face each other across a small gap and a specific voltage is applied between two electrodes one laminated to the photo-conductive layer another laminated to the charge holding layer. The former electrode is transparent, and the optical image is projected to the photo-conductive layer member through the transparent electrode, and the charge latent image formed on the photo-conductive layer member in response to the projection of the optical image, is transferred onto the surface of the charge holding layer member by a spark discharge caused in the small gap.
The charge latent image formed firsty on the surface of the photo-conductive layer member has a high resolution. However, it is very difficult to transfer the charge latent image without losing the high resolution to the charge holding layer member through the gap, due to undesirable divergence of electric flux lines generated from charges of the charge latent image, which extend to the charge holding layer member.